Biological control as a tactic of environmentally safer agriculture has not been widely accepted by farmers. In Japan integrated biological control with native natural enemies is rapidly developing for greenhouse vegetables, because of high prices of commercially mass-reared biological control agents. We have studied the effective use of natural enemies at farm level, focusing on generalist predators, although there are differences in using natural enemies for augmentation in greenhouses and conservation in open fields. Recently, however, insectary plants (crops) have been considered as a key component for enhancing natural enemies. We have examined the effectiveness of candidate insectary plants on natural enemies and implemented biointensive IPM with insectary plants at farm-level. Our recent study suggested that some herbs and crops are highly effective on improving the survival and reproduction of generalist predators. By growing such plants in vegetable greenhouses and open-fields, natural enemy populations could be enhanced and thus stably persist even after targeted prey populations are exploited. Moreover, insectary plants may result in a shift of IPM from level I to level II.